1. Field of the Invention
The present invention relates to tamper resistant caps for containers and particularly to a cap for a threaded container which provides a positive indicator device to clearly show that the container has been opened previously or that the cap has been tampered with.
2. Description of the Prior Art
Various packaging devices have included means to ensure that the contents are sealed against contamination. These include simple adhesive seals over the container opening under the cap, breakable sections which remain on the neck when the cap is twisted off and plastic enclosures which must be removed for access to the cap. In many cases, the caps can be replaced and there is no indication that the container was previously opened or tampered with. In view of recent incidents involving poisoning of medications and foods, it has become more urgent to find improved cap sealing and indicator devices. Examples of such known prior art devices are found in U.S. Pat. No. 4,572,389 wherein an external satellite band is secured to a cap by a flange or struts which are broken when the cap is twisted off. Removal of the band reveals the fractured portions and indicates a previous opening. U.S. Pat. No. 4,570,810 shows another band secured between a bottle neck and a cap which reguires breaking and removal of the inner member to display signs of tampering. In U.S. Pat. No. 4,456,139, a transparent wall portion of a cap permits visual observation of a broken seal. A further variation appears in U.S. Pat. No. 4,444,328 wherein a container and closure have openings which are out of alignment in a closed position and moved into alignment in an open position. Visual indicia provide indication of a safe unopened position. An arrangement of cams and stops prevent return of the closure into the first position. These various devices however do not provide sufficiently clear and direct evidence of prior use or tampering, are relatively inefficient and complex, and often require parts that can only be used with special enclosures rather than screw type caps that engage threaded necks of standard containers.